Multistage liquid driven ejector for delivering liquids



' Patented Mar. 21, 1933 UNITED STATES PAUL SCHMIDT, OI MUNICH, GERMANYIULTISTAGE LIQUID DRIVEN EJ'ECTOR FOR DELIVERING LIQUIDS Applicationfiled August 10, 1932, Serial No. 628,247, and in Germany August 1}},I931.

' In addition to the well known ways of deliverin liquids by means ofreciprocating or centri ugal' pumps, a number of methods of deliveryhave become known, the use of which, in special cases, afl'ords specialadvanta es. Among these different methods of de ivery, some use has beenmade of deliveriyl by the so-called Mammut pumps (in whic air or gas isintroduced at the lower end of the immersed delivery pipe for thepurpose of forming a mixture of gas and liquid in the delivery pipe) andalso of methods employing steam injectors, hydraulic rams and uniformlyacting liquid ejectors.

The present invention relates to a particularly advantageous embodimentof this last named device, that is to say, of the uniformly acting,liquid driven e ector for the delivery of liquids. The embodimentaccording to the present invention ensures the delivery of liquids byejector action even to the greatest delivery heights occurring inpractice, whereas, as is well known, it has not hitherto been possibleto overcome very great delivery heights (many hundreds of metres forexample) by ejectors. It is true that the literature on the subjectcontains certain suggestions for the construction and use of ejectorsfor these purposes, (among others, the suggestion to use a multi-stagearrangement) but none of these suggestions could be successfully carriedout in practice.

The difficulties attending the practical working of ejectors of thiskind will now be demonstrated with reference to the graphs shown inFigs. 1, 2 and 3 of the accompanying drawing, Fig. 4 of which showsdiagrammatica I a two-stage ejector constructed according to the presentinvention.

Fig. 1 shows, for comparison with the ejector according to the presentinvention, the output curve H of a single stage ejector of the normalconstruction such as has been quite usual heretofore. The correspondinefliciencies at various outputs are denote by the curve n.

Thus curve H shows the height of delivery for various differentquantities of liquid raised, while the curve n gives the correspondingdegrees of efliciency for the various .be observed that both thesecurves follow PATENT OFFICE- quantities and at the various deliveryheights plotted in curve H. This customary method of representing theoutput of an ejector shows fully and exactly how the apparatus behavesunder working conditions.

In Fig. 1 the curve H extends only over a range of comparatively lowdelivery heights and comparatively large volumes of liquid delivered. Atthese outputs, which have been customary heretofore with uniformlyacting ejectors, relatively high efliciencies have been obtained and nodifliculties have been experienced in practical working.

N ow Fig. 2 shows the output curve of an ejector for very great heightsof delivery, amounting to many hundreds of metres. Here, again, theoutput curve (height of .delivery plotted against quantity of liquidde-v livered) is denoted by H and the corresponding efiiciency curve byn, as in Fig. 1. It will courses very different from those of the H Iand n curves for a normal ejector (Fig. 1). Thus in the course of alarge number of experiments, it has been found that ejectors of thiskind, which are desi ed to deliver relatively small quantitieso liquidto very great heights, in man cases give no normal output curve at all.n the contrary even at the smallest delivery the action of the driv- 8oing jet suddenly ceases,'so that this value of the delivery cannot beexceeded without further aid. In the output curve shown in Fig. 2 thispoint is denoted by 1. It should be noted that the output curve breaksoff even befone the ejector has reached its normal output. j Accordingto the measurements made of ejectors which have actually beenconstructed, this falling off, or breakdown must be attributed to adeviation from the normal pressure at the entrance to the diffuser ofthe ejector. At this region there is set up apartial vacuum which tendsto draw the current of liquid away from the walls and naturally thisresults in a corresponding restriction of the free cross sectional areaand throttles 011' any further su ply ofliquid.

It has now en found that by the provision of two or more stages of apeculiar construction the disadvantage illustrated by the curves. in Fi2 can be obviated. Accordingly, the su ject matter of this invention isa multi-stage liquid driven ejector for the deliver of liquids,particularly of rock oil from eep bore holes, the feature of which isthat, in the first stage, the magnitude of the exit cross sectional areaof the driving nozzle is less than 0.5 of the size of the smallest crosssectional area of the difiuser, and that in the second stage, the sizeof the exit cross sectional area of the driving nozzle is more than 0.6of the size of the smallest cross sectional area of the difi'user. Amulti-stage ejector according to the invention may comprise two or morestages.

The advantageous action of these multistage ejectors, according to theinvention, is shown by the curves given in Fig. 3, in which,

, as in Figs. 1 and 2, the output curve is denoted by H while thecorresponding efliciencies are shown by,the curve n.

This Figure 3 shows the H and n values obtainable with a twostageejector, constructed according to this invention and operating todeliver very small quantities of liquidto very great heights (aspreviously attempted with the single-stage pump the curves of which aregiven in Fig. 2 Now, on comparing Fig. 3 with Fig. 2, it can be seenthat, by arranging the cross sectional areas of the jet nozzles anddifi'users according to the present invention the curve of deliveryheight H and the efiiciency curve-can be made to assume a normal coursesomewhat similar to that obtained with an ordinary ejector (c. f. Fig.1). The important difference, however, between the ejector to which Fig.1 applies, and the ejector according to this invention is that the newconstruction makes it possible to reach hitherto unattainable heights ofdelivery with relatively very small quantities of liquid delivered. Inapparatus according to the invention the output from the first stage isvery small per se, so that this first stage forms, as it were, onlypreliminary stage to. the

. second or main stage, which supplies by far the greater part of thetotal output.

By the interpolation of the first stage the liquid to be delivered issupplied to the second or main stage at a certain initial -pressure. Inthis way the formation of cavities or the separation of the liquidstream from the walls at the'entrance to the .difiuser is effectivelyavoided, so that a normal output the relationship.

nozzle is denoted by 4. The jet of liquid from the nozzle 3 flows intothe diffuser 5, the smallest cross sectional area of which is denoted by6. The exit cross sectional area 4 of the driving nozzle 3 is less than0.5 of .the smallest cross sectional area of the diffuser 5, as denotedby 6. The delivered liquid issues from the difiuser 5 together with thedriving liquid delivered through the nozzle 3, both passing upwards tothe second stage of the ejector. The driving nozzle of the second stageis denoted by. 7 and the exit cross sectional area of this drivingnozzle 7 is indicated b 8. The liquid issuing from the nozzle 7 ows,together with the liquid delivered from the first stage into thediffuser 9 of the second stage." The smallest cross sectional area ofthis diffuser 9 is indicated by 10. The exit cross sectional area 8 ofthe nozzle 7 is, according to this invention, more than 0.6 of thesmallest cross sec- ?)ional area of the diffuser 9, as indicated It willbe seen from the action of the two stages arranged in series that in allcases the second stage must be placed comparativelv close to the'firststage and, in general, the first two stages of any ejector according tothis invention must be placed conjointly at the beginning of a deliverypipe.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the sameis to be per- 7 size of the-exitcross sectional area of the drlving nozzle is more than 0.6 oftlfe sizeof the smallest cross sectional area of the diffuser.

In testimony whereof I have signed my name to this specification.

' PAUL SCHMIDT.

